1. Field of the Invention
This invention relates to a piezoelectric element configured such that a piezoelectric property is improved by controlling crystal orientation of a piezoelectric film using lithium potassium sodium niobate and a piezoelectric device.
2. Description of the Related Art
A piezoelectric material is processed so as to form various piezoelectric elements in accordance with a variety of the intended uses, in particular, is widely used as a functional electronic component such as an actuator that allows an object to be changed in shape when an electric voltage is applied thereto, a sensor that generates an electric voltage due to the change in shape of the element reversely.
As the piezoelectric material that is used for the application of the actuator and the sensor, a lead-based dielectric material that has an excellent piezoelectric property, in particular, a Pb(Zr1-XTiX)O3 based perovskite type dielectric material that is referred to as a PZT has been widely used, normally the PZT dielectric material is formed by sintering an oxide comprised of an individual element.
In addition, recently, in terms of environmental consideration, it is desired that a piezoelectric material that is lead-free is developed, and it is in progress to develop lithium potassium sodium niobate represented by a general formula of (NaxKyLiz)NbO3 (0<x<1, 0<y<1, 0<z<1, x+y+z=1) or the like. The lithium potassium sodium niobate has a piezoelectric property comparable to the PZT, thus the niobate is expected as a strong candidate of a lead-free piezoelectric material.
On the other hand, at present, various electronic components become more downsized and upgraded, thus it is strongly needed for the piezoelectric element to be downsized and upgraded. However, a piezoelectric material manufactured by a conventional manufacturing method such as a sintering method, particularly if it has a thickness of not more than 10 μm, is configured to have a thickness that is close to the size of the crystal grain constituting the material, thus the influence thereof cannot be ignored. Consequently, a problem is caused that variation and deterioration in the property become prominent, thus in recent years, for the purpose of preventing the problem, a forming method of a piezoelectric film in which a thin film technology and the like are applied instead of the sintering method has been investigated.
Recently, a PZT thin film formed on a silicon substrate by a RF sputtering method is put into practical use as an actuator for a head of a high-definition and high-speed ink-jet printer (for example, refer to JP-H10-286953 A1 and “High performance piezoelectric material and advancing applied technology” supervising editor: Kiyoshi Nakamura, published by Science & Technology, 2007).
In addition, a piezoelectric film that is represented by a general formula of (NaxKyLiz)NbO3 and has a high orientation in a particular plane direction is also proposed as a piezoelectric element of lithium potassium sodium niobate that is lead-free (for example, refer to JP-A-2007-019302). According to JP-A-2007-019302, for example, the piezoelectric film formed by a sputtering method can be lead-free and obtain an excellent piezoelectric property.